1. Field of the Invention
The present invention relates to electrographic stylus recording apparatus for the recording of toner images on a recording medium wherein a plurality of magnets are adapted for rotation within a nonrotatable cylindrical sleeve with the recording stylus array for the apparatus mounted on the outer surface of such sleeve, the invention relating to structure providing for removal of excess and nonimaging toner from the sleeve and the manner in which the stylus array and associated electrical conductors are mounted relative to the toner dispensing apparatus.
2. Description of the Prior Art
U.S. Pat. No. 3,879,737 to Lunde discloses an electrographic stylus recording apparatus for the recording of toner images wherein a plurality of magnets are adapted for rotation within a nonrotatable cylindrical sleeve with the recording stylus array for the apparatus mounted on the outer surface of such sleeve. FIG. 3 of the patent shows how the electrical conductors for the stylus array are brought to and extend beyond the ends of the sleeve for connection to driver circuits used with the stylus array. Since the toner that is carried about the sleeve due to the rotation of the magnets within the sleeve moves about the entire circumference of the sleeve, it is necessary that the electrical conductors for the stylus array be brought to and extend beyond the ends of the sleeve. This arrangement presents a problem with respect to the use of etching technology for forming the electrical conductors. When a high density stylus array is to be used, such as 80 styli per centimeter, the length required for the conductors for an arrangement as disclosed in the Lunde patent is typically too great for the amount of reduction that is needed for the art work used in an etching process. In addition, the apparatus of the Lunde patent provides little control over the amount of toner material that is brought to the sleeve on which the stylus array is mounted. It has been found also that such an arrangement for bringing the toner material to the recording region at the stylus array does not provide adequate control of the amount and movement of the toner material to the recording region particularly when a high density stylus array is used.
U.S. Pat. No. 3,946,402 to Lunde discloses a toner applicator arrangement which overcomes the toner material control deficiency of the apparatus disclosed in the first above-mentioned U.S. patent to Lunde. The apparatus disclosed in U.S. Pat. No. 3,946,402 accurately meters an optimum level of toner from a toner supply onto a recording member which moves to present the toner material to a recording region presented between the recording member and a stylus array allowing high quality, high resolution toner images to be formed. Excess toner plus nonrecorded or unused toner material is magnetically removed from the recording member and from the recording region at the stylus array by rotating magnets within a cylindrical sleeve on which the stylus array is mounted. The removed toner moves over the surface of the sleeve to a blade which scrapes the toner from the sleeve allowing it to fall by gravity back to the toner supply hopper. Since the recording member is pre-toned by this arrangement to bring toner to the recording region, considerable nonimaging background toner material remains on the recording member, particularly on recording members presenting a relatively rough surface, such as paper. In addition, such an arrangement does not provide a solution to the problem presented with respect to disposition of the electrical leads for a high density stylus array.